Outer Loop Power Control for E-DCH

ABSTRACT

The present invention relates to a method and an enhanced uplink (UL) telecommunication system for power control. The system comprises at least one first radio network controller (RNC) and at least one first and one second base station enabling wireless communication with at least one first user terminal. The first and the second base stations receive at least a first transport block (TB), the first TB being transmitted by the user terminal over an established communication channel. If the received first TB includes at least one error, the base station that found the error controls the number of decoding attempts for the first TB. If the first TB is a discontinuous transmission frame (DTX), the base station resets a decoding attempt counter and prepares the first and second base stations for a new, second TB.

TECHNICAL FIELD

The present invention relates to a method and a telecommunication systemfor power control, and a base station in the system enabling saidmethod.

BACKGROUND

There is an increasing need of delivering wireless technology withbroadband capacity for cellular networks. A good broadband system mustfulfil certain criteria, such as high data rate and capacity, low costper bit, good Quality of Service and greater coverage. High Speed PacketAccess (HSPA) is an example of a network access technology that enablesthis.

HSPA is a collection of protocols which improves the performance ofexisting Universal Mobile Telecommunication Systems (UMTS), which is athird generation (3G) cell phone technology. UMTS uses Wideband CodeDivision Multiple Access (WCDMA) as air interface for the radio-basedcommunication between user equipment (UE), in form of a mobile terminal,and the base station (BS). The air interface in the Open SystemsInterconnection (OSI) model comprises layers 1 and 2 of the mobilecommunications system, establishing a point-to-point link between the UEand a radio access node (RAN).

HSPA is an integral part of WCDMA. Wide-area mobile coverage can beprovided with HSPA. It does not need any additional spectrum orcarriers. Currently, WCDMA can provide simultaneous voice and dataservices to users on the same carrier. This also applies to HSPA whichmeans that spectrum can be used efficiently. Simulations show that in amoderately loaded system, HSPA can largely reduce the time it takes todownload and to upload large files. The primary benefits of HSPA areimproved end-user experience. In practice, this means shorter UL and DLtimes as a result of higher bit-rates and reduced latency compared toearlier releases of WCDMA. HSPA also benefits operators by reducing theproduction cost per bit. More users can be served with higher bit-ratesat lower production costs.

HSPA is the set of technologies defining the migration path of WCDMAoperators worldwide. The two existing features, High Speed DownlinkPacket Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), inthe HSPA family provides the increased performance by using improvedmodulation schemes and by refining the protocols by which handsets andbase stations communicate. These improvements lead to the betterutilization of the existing radio bandwidth provided by UMTS.

High Speed Downlink Packet Access (HSDPA) is the first feature withinHSPA. It is part of the WCDMA Third Generation Partnership Project(3GPP) Release 5 specification. HSDPA provides a new downlink transportchannel that enhances support for high-performance packet dataapplications. It represents the first step in the evolution of WCDMAperformance. HSDPA can deliver an up to 35 fold increase in downlinkdata rates of standard WCDMA networks, enabling users to access theInternet on mobile phones and laptops, at speeds previously associatedwith fixed line DSL.

HSDPA is based on shared channel transmission, which means that somechannel codes and the transmission power in a cell are seen as a commonresource that is dynamically shared between users in the time and codedomains for a more efficient use of available codes and power resourcesin WCDMA. The radio channel conditions experienced by different downlinkcommunication links vary significantly, both in time and betweendifferent positions in the cell. To compensate for rapidly varying radioconditions in the downlink, HSDPA relies on bit-rate adjustment. Thatis, while keeping transmission power constant, it adjusts (by lowering)the data rate by adjusting the modulation.

Along with the HS-DSCH (High Speed Downlink Shared Channel) physicalchannel on which payload data is sent, three new physical channels arealso introduced: HS-SCCH, HS-DPCCH and HS-PDSCH. The High Speed-SharedControl Channel (HS-SCCH) informs the user that data will be sent on theHS-DSCH 2 slots ahead. The Uplink High Speed-Dedicated Physical ControlChannel (HS-DPCCH) carries acknowledgment information and currentchannel quality indicator (CQI) of the user. This value is then used bythe base station to calculate how much data to send to the user deviceson the next transmission. The High Speed-Physical Downlink SharedChannel (HS-PDSCH) is the channel mapped to the above HS-DSCH transportchannel that carries actual user data.

High Speed Uplink Packet Access (HSUPA) is the second feature withinHSPA. It is part of the WCDMA Third Generation Partnership Project(3GPP) Release 6 specification. HSUPA provides a new uplink (UL)transport channel called Enhanced Dedicated Channel (E-DCH). HSUPAdramatically increases the uplink data traffic rate. This technology islikely to significantly increase the amount of data uploaded over mobilenetworks, especially user-generated content. Although a lot of it isdownlink oriented, there are still quite a number of applications thatwill benefit from an improved uplink. These include the sending of largee-mail attachments, pictures, video clips, blogs etc. HSUPA is alsoknown as Enhanced UL. In contrast to HSDPA, the new uplink channel thatis introduced for Enhanced Uplink is not shared between users, but isdedicated to a single user.

FIG. 1 shows a HSUPA network overview. A user terminal 15 communicateswith the core network CN via at least one base station 11. The systemfurther comprises a second base station 10 with a corresponding system.A first radio network controller RNC 12 establishes an E-DCH whichenables uplink data traffic from the user terminal to the base station.The E-DCH carries data for at least one radio network bearer. The term“lu” in FIG. 1 represents the interface between RNC and core network.The term “lub” represents the interface between RNC and the radio basesstation (RBS).

Several new physical channels are added to provide and supporthigh-speed data transmission for the E-DCH. As shown in FIG. 1, two newcode-multiplexed uplink channels are added:

-   -   E-DCH Dedicated Physical Data Channel (E-DPDCH)    -   E-DCH Dedicated Control Channel (E-DPCCH)

E-DPDCH carries the payload data, and the E-DPCCH carries the controlinformation associated to the E-DPDCH. E-DPDCH is used to carry theE-DCH transport channel. There may be zero, one or several E-DPDCH oneach radio link wherein there is at most one E-DPCCH on each radio link.E-DPDCH and E-DPCCH are always transmitted simultaneously. E-DPCCH shallnot be transmitted in a slot unless E-DPDCH is also transmitted in thesame slot.

Similarly, three new channels, see FIG. 1, are added to the downlink forcontrol purposes:

-   -   E-DCH Hybrid Automatic Repeat Request (HARQ) Indicator Channel        (E-HICH) carrying the uplink E-DCH hybrid Acknowledgement (ACK)        and Negative ACK (NACK) indicator.    -   E-DCH Absolute Channel (E-AGCH) carrying absolute grants, which        means that it provides an absolute limitation of the maximum        amount of uplink resources the UE may use.    -   E-DCH Relative Grant Channel (E-RGCH) carrying the uplink E-DCH        relative grants, which means that it controls the resource        limitations by increasing or decreasing the limitations with        respect to the current serving grant.

E-AGCH is only transmitted from the serving cell. E-RGCH and E-HICH aretransmitted from radio links that are part of the serving radio link setand from non-serving radio links.

As shown in FIG. 1 the same E-DCH can be provided both through the firstRNC 12 for the serving cell and through a second RNC (RNC2) 13 for thenon-serving cell. The second RNC 13 serves a separate base station 10with a Node B NB2 and an enhanced UL scheduler (EUL-S2). Except forE-AGCH (which can only be transmitted through the serving cell) all thephysical channels can be transmitted through either of the cells. As analternative one RNC can serve both a serving cell and a non-servingcell. The term “Iur” in FIG. 1 represents the interface between thefirst RNC 12 and the second RNC 13. Only one RNC will communicate withthe core network (e.g. the first RNC). The first RNC is in control ofthe connection and handles things like soft handover.

Note that HSUPA channels are added on top of uplink/downlink dedicatedchannels. Each UE 15 therefore additionally carries an uplink anddownlink dedicated physical channel (DPCH), see FIG. 1. In the downlink,a fractional dedicated channel (F-DPCH) can be used alternatively. TheF-DPCH carries control information and is a special case of downlinkDedicated Physical Control Channel (DPCCH). UL might only contain theDPCCH as in FIG. 1. It could also contain a Dedicated Physical DataChannel (DPDCH). The F-DPCH has been introduced in 3GPP release 6 inorder to optimize the downlink codes usage.

Soft handover refers to the feature used in WCDMA standards, such asHSUPA technology. In soft handover the user terminal 15 issimultaneously connected to two or more cells, such as the cells servedby the base stations 10 and 11. It is a form of mobile-assisted handoverin which the user terminal measures the power from different cells andrequests a handover if needed. It is with WCDMA possible tosimultaneously receive signals from both base station 10 and basestation 11. The user terminal can combine the signals from both stationsand/or select the signals with the highest quality.

In HSUPA, the Node B NB/NB2 in the base stations 10, 11 send the bitstream from the mobile terminal to the RNC 12 together with informationabout the quality of the received bits. The RNC examines the quality ofthe bit streams and selects the stream with the highest quality. Fromnow on the term “base station” will be used, even though the Node BsNB/NB2 in the base stations 10, 11 that actually performs most of thesteps. From now on there will also be reference only to the RNC 12,since the RNC2 13 forwards the information to the RNC 12 and the RNC 12performs the actual power control

The RNC 12 may also use a power control method to control the transmitpower that the user terminal 15 is using when the quality of thereceived bit stream is too low. There is an inner loop power controlmethod between the base station 10, 11 and the user terminal, which isbased on a signal to interference ratio (SIR) target. The base station10, 11 measures continuously SIR of a physical channel (DedicatedPhysical Control Channel—DPCCH) transmitted by the user terminal 15. SIRrelates to the fact that a certain DPCCH channel power in needed inrelation to the interference so that the system is able to decode a datapacket. SIR is the quotient between the average received modulatedcarrier power and the average received co-channel interference power,e.g. cross-talk from other transmitters than the useful signal.

This real time SIR measured is compared to the SIR target, which isprovided by the RNC 12. The base station 10, 11 transmits a powercontrol (TPC) command in a downlink to the user terminal 15 to increaseor decrease the transmit channel power level so that the real time SIRmeasured is controlled towards the SIR target. With this power control,the signals from different user terminals can be received with therequired quality at changing conditions.

The inner loop power control is dependent on an outer loop power control(OLPC). The SIR target is set in the OLPC by the RNC 12. The OLPC is aquality control loop in the RNC. It typically operates on information onthe number of decoding attempts needed by the user terminal 15 forsuccessful decoding of a transport block (TB). A TB may be a group ofbits decoded for the error control or a string of records treated as aunit. A block decoding attempt ends either in a decoding failure(non-successful decoding) or a successful decoding. In soft handover theuser terminal 15 will stop transmitting a particular TB as soon as ithas been acknowledged (successfully decoded) by any cell involved in thehandover.

A hybrid automatic repeat request (HARQ) may be used for controlling thequality of the signalling from the user terminal 15 performed bydecoding TBs. In HARQ, when coded TB is received by the base station 10,11, the station first decodes the TB. If there is a decoding failure(the channel quality is bad and not all transmission errors can becorrected), a retransmission of the particular TB is requested by thestation. When HARQ is used, a sequence number Reception Sequence Number(RSN) is reset to zero when new data (a new TB) is transmitted. If theTB cannot be decoded, the RSN is stepped up. It is further stepped upfor every failed decoding of the particular TB, to a maximum value ofe.g. 3. The HARQ failure indication is described in 3GPP TS 25.427.

In WO 2006/016230 a failure indication method is disclosed. When amaximum number of decoding attempts (repeated) are reached for aparticular TB, a failure indication is sent to the RNC 12. The TBs witherrors (so called “erasures”) received are stored in the meantime andtransmitted with the failure indication. The RNC checks the Block ErrorRate (BLER) ratio on the TBs forwarded from the station 10, 11 atfailure indication and determines the SIR target in the OLPC on thebasis of the BLER. In particular, the RNC compares the BLER of thereceived TB with a target BLER (determined based on the QoS (Quality ofService) for a particular service) and step up the SIR target if thereceived BLER is higher the target BLER.

The new SIR target is forwarded to the base stations 10, 11 and the userterminal 15. Since a maximum number of decoding attempts are defined,the base station 10, 11 will not notify the RNC about every failure.Thereby, the RNC will not increase the SIR target unnecessarily andconsequently waste of channel capacity and transmission power isavoided.

In U.S. Pat. No. 7,224,993, a power control method is disclosed in whicha discontinuous transmission mode (DTX) frame is detected in a channel.DTX is a mode of operation in which the station 10, 11 or the userterminal 15 switches is transmitted on or off automatically (withoutreleasing the channel) when no data is sent to save channel capacity andtransmission power and decrease interference. In DTX mode unannouncedframes are transmitted with a similar SIR as erasures, and there is arisk that the base station at low signal strength detects the DTX framesas erasures, since they are unannounced.

This eventually leads to an unnecessary repetition of the frame(requested by the base station) and/or an increase of SIR target by theRNC (resulting in an increased transmittal power) when notified (failureindication) by the base station. The problem is solved by separatingerasures (TB errors) from DTX frames by looking at a sequence number(RSN) included e.g. in a protocol header for the delivered packet.Information over a radio link protocol (RLP) is evaluated to determineif the frame is correct, is an erasure or a DTX frame.

Sometimes only a small amount of data is sent infrequently and theconnection is in soft handover. This is for instance in ping or whensome other “keep-alive” signalling is performed. The following scenariomay then occur:

-   -   If the TB is successfully decoded in one of the cells        (non-serving cell), for instance served by the base station 10,        and the user terminal 15 receives the acknowledgement it will        stop transmitting the particular TB.    -   The base station 11, serving the other cell (serving cell), will        eventually send a HARQ indication (failure indication) to the        RNC 12 and indicate that the TB has not been decoded despite the        maximum number of decoding attempts (see WO 2006/016230).    -   This may trigger an increase of the SIR target for no good        reason at all, since the TB was actually decoded by the base        station 10 of the non-serving cell.

This is illustrated in FIG. 2 showing an overview of the existingsolution for OLPC. First transmission 1A of the TB fails in the servingcell where the serving radio link (RL) is present. The first decodingattempt with non-successful decoding is illustrated by a cross in thefirst square from the left. This cell is served by the base station 11.The base station then asks the station to repeat the particular TB.However, when no successful decoding takes place within the time of themax number of decoding attempts (in total four in this example,illustrated by four squares), a HARQ Failure indication 3A is sent tothe RNC, eventually together with the last TB received (or optionallyall TBs stored since the first attempt).

Simultaneously, the user terminal 15 also transmits 1B the particular TBto the non-serving cell served by the base station 10. The firstdecoding attempt of the TB is successful (decoded OK)=>no moreretransmissions from the user terminal. This is illustrated by a pattern(chess pattern) in the first square from the left. The base station 10then transmits 3B a Cyclic Redundancy Check (CRC) OK confirmationtogether with the TB to the RNC 12.

The RNC 12 receives both sequences of received TB from the base stations10, 11 via lub, which are combined to a single sequence 4 with the TBwith no error and the error TB. The single sequence for instancerepresents the TBs received, decoded and sent to the RNC by the basestations.

FIG. 3 shows an OLPC example. When the base station 11 does not manageto decode the TB and transmits a failure indication (HARQ) to the RNC12, reference A, SIR target (y-axis) is stepped up 5A (a large step).Every time the RNC receives information (CRC OK confirmation) the SIRtarget is stepped down 5B a small step.

With the scenario described it is not possible to determine based on thesequence number in upcoming transmissions whether another base station,e.g. base station 10, has managed to decode (successful decoding) theTB. Therefore, the solution described in U.S. Pat. No. 7,224,993 is notuseful.

SUMMARY

The object of the present invention is to solve the above problemrelating to the described scenario, by a method and a telecommunicationsystem for power control, and a base station in the system enabling saidmethod.

The problem is solved by means of a method for power control in anenhanced uplink (UL) telecommunication system. The system comprises atleast one first radio network controller (RNC) and at least one firstand one second base station enabling wireless communication with atleast one first user terminal. The first and the second base stationsreceive at least a first transport block (TB), the first TB beingtransmitted by the user terminal over an established communicationchannel. The first and the second base station then controls whether thereceived first TB includes at least one error. If at least one error inthe first TB is found by the first and/or the second base station, thebase station/-s that found the error further controls the number ofdecoding attempts for the first TB, the number of decoding attemptsbeing stored in a decoding attempt counter.

What particularly characterizes the method according to the presentinvention is that if the number of decoding attempts for the first TB isequal to a decoding attempt threshold, the base station/-s that foundthe error further determines if the first TB is a discontinuoustransmission frame (DTX) or a TB including errors. If the basestation/-s determines that the first TB is a DTX, the base station/-sthat found the error further resets the decoding attempt counter andprepares the station/-s for a new, second TB.

The problem is also solved by means of a base station adapted for powercontrol in an enhanced uplink (UL) telecommunication system. The systemfurther comprises at least one first radio network controller (RNC), atleast one first and one second base station in the system enableswireless communication with at least one first user terminal. The firstand the second base stations are adapted to receive at least a firsttransport block (TB), the first TB being transmitted by the userterminal over an established communication channel. The first and thesecond base station are further adapted to control whether the receivedfirst TB includes at least one error. If at least one error in the firstTB is found by the first and/or the second base station, the basestation/-s that found the error are further adapted to control thenumber of decoding attempts for the first TB, the number of decodingattempts being stored in a decoding attempt counter.

What particularly characterizes the base station according to thepresent invention is that if the number of decoding attempts for thefirst TB is equal to a decoding attempt threshold, the base station/-sthat found the error is further adapted to determine if the first TB isa discontinuous transmission frame (DTX) or a TB including errors. Ifthe first TB is a DTX, the base station/-s that found the error isfurther adapted to reset the decoding attempt counter and prepares thestation/-s for a new, second TB.

The problem is finally solved by means of an enhanced uplink (UL)telecommunication system adapted for power control. The system comprisesat least one first radio network controller (RNC) and at least one firstand one second base station enabling wireless communication with atleast one first user terminal. The first and the second base stationsare adapted to receive at least a first transport block (TB), the firstTB being transmitted by the user terminal over an establishedcommunication channel. The first and the second base station are furtheradapted to control whether the received first TB includes at least oneerror. If at least one error in the first TB is found by the firstand/or the second base station, the base station/-s that found the errorare further adapted to control the number of decoding attempts for thefirst TB, the number of decoding attempts being stored in a decodingattempt counter.

What particularly characterizes the system according to the presentinvention is that if the number of decoding attempts for the first TB isequal to a decoding attempt threshold, the base station/-s that foundthe error is further adapted to determine if the first TB is adiscontinuous transmission frame (DTX) or a TB including errors. If thefirst TB is a DTX, the base station/-s that found the error is furtheradapted to reset the decoding attempt counter and prepares thestation/-s for a new, second TB.

Since DTX is determined by the base station and the counter is reset ifDTX is determined an unnecessary increase of the SIR target for E-DCH bythe OLPC in the RNC is avoided. Thereby excessive transmit power fromthe user terminal is avoided.

BRIEF DESCRIPTION OF DRAWINGS

In the following text the invention will be described in detail withreference to the attached drawings. These drawings are used forillustration only and do not in any way limit the scope of theinvention:

FIG. 1 shows a HSUPA network overview.

FIG. 2 shows the receiving, decoding and sending of TBs in a HSUPAnetwork.

FIG. 3 shows the OLPC in dependency on the received, decoded and sentTBs.

FIG. 4 shows the main code for OLPC according to the present invention.

FIG. 5 shows the DTX detection code according to the present invention.

FIG. 6 shows the receiving, decoding and sending of TBs in a HSUPAnetwork with the proposed improvement according to FIG. 4-5.

DETAILED DESCRIPTION

The invention will now be described in detail with reference toembodiments described in the detailed description and shown in thedrawings.

The embodiments refer to a method and a telecommunication system forpower control, and a base station in the system enabling said method.The system and the base station in the system are adapted to perform themethod steps as described in the method. It should be understood by aperson skilled in the art that the fact the system and in particular thesystem parts perform a method step means that it is adapted to performsaid step. This is enabled by introducing a new mechanism into thesystem parts, the new mechanism performing the method steps describedherein.

FIGS. 1, 2 and 6 shows a HSUPA network overview. A user terminal 15communicates with the core network CN via a first base station 11 and asecond base station 10. FIGS. 1 and 2 has also been described in thebackground part. A radio network controller RNC 12 establishes anEnhanced Dedicated Channel (E-DCH) which enables uplink data trafficfrom the user terminal 15 to the base station, the E-DCH carrying datafor at least one radio access bearer (RAB).

The system comprises at least one first radio network controller RNC 12which manages and controls at least one first 11 and one second 10 basestations. It is also the link between the bases stations and the CoreNetwork CN. The base stations comprises a Node B NB/NB2 and (since it isa HSUPA system) an Enhanced UL Scheduler EUL-S. The base stationsfurther comprises antennas enabling wireless communication with at leastone first user terminal (15). The system is shown in FIG. 1, 2, 6 anddescribed in the background part.

The first 11 and the second 10 base stations receive 1A, 1B, see FIGS. 2and 6, at least a first transport block (TB). The first TB istransmitted by the user terminal 15 over an established communicationchannel (E-DCH). A TB may be a group of bits decoded for the errorcontrol or a string of records treated as a unit. A TB is the smallestdata packet (for a certain configuration) which can be sent in aTransmission Time Interval—TTI. In E-DCH there is only one TB in eachTTI, while in other types of transport channels a TTI can contain morethan one TB (for example four TB of 336 bits each over a TTI of 20 msresults in a bit rate of 64 kbps).

The first and the second base stations 10, 11 controls whether thereceived first TB includes at least one error. Hybrid Automatic RepeatRequest—HARQ is preferably used for controlling the quality of thesignalling from the user terminal 15 performed by decoding TBs. In HARQ,when coded TB is received 1A, 1B by the base station 10, 11, the stationfirst decodes the TB. If there is a decoding failure (the channelquality is bad and not all transmission errors can be corrected), aretransmission of the particular TB is requested by the station. Thetransmission and retransmission of TB for block decoding attempts endseither in a decoding failure (non-successful decoding) or a successfuldecoding as will be described.

If no error in the first TB is found by the first 11 and/or the second10 base stations (successful decoding), the base station/-s transmit 3B,see FIG. 2, a success indication to the RNC, comprising the first TBcontaining no errors. In soft handover (which the present inventionrelates to) the user terminal 15 will stop transmitting a particular TBas soon as it has been acknowledged (successfully decoded) by any basestation involved in the handover.

If at least one error in the first TB is found by the first 11 and/orthe second 10 base stations, the base station/-s that found the errorfurther controls the number of decoding attempts for the first TB. Thenumber of decoding attempts is stored in a decoding attempt counter.When HARQ is used, a sequence number Reception Sequence Number (RSN) isreset to zero when new data (a new TB) is transmitted. If the TB cannotbe decoded, the RSN is stepped up in the decoding attempt counter andHARQ requests a retransmission of the TB. The counter is then furtherstepped up for every failed decoding of the particular TB, to a maximumvalue of 3. The number of retransmissions of a particular TB occurs atwell defined occasions. For a TTI of 10 ms, it occurs every fourth TTI,and for a TTI of 2 ms every eighth TTI.

Retransmissions 1A/1B of the first TB occurs at certain times TTIrelative to the first transmission. Since the TB is retransmitted forexample every fourth or eight TTI the counter may either count time ornumber of decoding attempts.

The problem with the known power control solutions is that at periodswhen a small amount of data is transmitted infrequently and theconnection is in soft handover (at least two base stations between whichthe user terminal is handover) a certain scenario may occur. The TB maybe successfully decoded by one base station 10 without the other basestation 11 being informed. The other base station will send a failureindication after the number of decoding attempts reaches a decodingattempt threshold, which triggers a step-up, see FIG. 3, of SIR targetfor no good reason. This is solved by the following method steps.

If the number of decoding attempts for the first TB is equal to adecoding attempt threshold 2C, the base station/-s 10, 11 that found theerror further determines 2D if the first TB is a discontinuoustransmission frame (DTX) or a TB including errors. If the basestation/-s 10,11 determines that the first TB is a DTX, the basestation/-s that found the error further resets 3C the decoding attemptcounter and prepares the station/-s for a new, second TB. This isillustrated in FIGS. 4 and 5.

DTX is continuously detected by the base stations 10, 11. However,nothing happens before the counter reaches the decoding attemptthreshold (e.g. value 3). The reset of the counter is the same procedureas when the TB is successfully decoded.

If the base station/-s 10,11 instead determines that the first TB is aTB that includes errors, the base station/-s 10,11 that found the errorfurther transmits 3A a failure indication to the RNC 12. The indicationcomprises the first TB including the error. The failure indicationpreferably consists in a Hybrid Automatic Repeat Request (HARQ) failureindication. The RNC then checks the Block Error Rate (BLER) ratio on thefirst TB transmitted from the base station/-s and determines a signal tointerference ratio (SIR) target on the basis of the BLER.

The scope of the present invention is to enable for the second basestation 10 to determine if the first TB has been successfully decoded ornot by the first base station 10. In accordance with the presentinvention, the first base station 11 interprets the DTX in theTransmission Time Interval (TTI), when the first TB would have beentransmitted, as an indication that the first TB has been successfullydecoded at least by the second base station 10. In soft handover (whichthe present invention relates to), the user terminal 15 will stoptransmitting a particular TB as soon as it has been acknowledged(successfully decoded) by any base station involved in the handover. ADTX is then sent at the TTI by the user terminal 15 instead of a TB.

When the first base station 11 interprets the transmission of the DTX asan indication of a successful decoding, it suppresses the sending of afailure indication to the RNC. This is illustrated by a cross over 3A inFIG. 6. This can be expressed as shown in FIG. 7 (for HARQ):

The suppression of the HARQ Failure Indication can preferably be donee.g. when the first base station is about to send 3A the indication tothe RNC 12.

The determination of DTX by the base station/-s 10, 11 that found theerror in the first TB is preferably at least based on the signalstrength or signal to noise ratio when transmitting the first TB. Thesignal strength or signal to noise ratio is determined by the basestation/-s (10, 11) by accumulating the received signal energy ormeasure the received signal power. A threshold for signal strength thatindicates the presence of DTX depends on whether the signal strength orthe signal to noise ratio is issued. FIG. 8 shows how this can beexpressed, as (for signal strength—SS or Signal to Noise ratio—SIR), seealso 2D in FIG. 5.

DTX detection is performed by accumulating received energy or measuringreceived power for the code or codes should be used for E-DCH. Theeasiest way is to measure on E-DPCCH since it has a fixed rate.

It will be appreciated by the person skilled in the art that variousmodifications may be made to the above-described embodiments withoutdeparting from the scope of the present invention. All such variousmodifications are included within the scope of the invention, which isthat the first base station interprets the DTX where a retransmissionwould have occurred as an indication that the TB has been successfullydecoded by another base station, and that there is no need to send aHARQ Failure indication.

1. A method for power control in an enhanced uplink (UL)telecommunication system comprising at least one first radio networkcontroller (RNC) and at least one first and one second base stationenabling wireless communication with at least one first user terminal,the method comprising: the first and the second base stations receivingat least a first transport block (TB), the first TB being transmitted bythe user terminal over an established communication channel; the firstand the second base station controlling whether the received first TBincludes at least one error; if at least one error in the first TB isfound by the first and/or the second base station, the base station thatfound the error further controls the number of decoding attempts for thefirst TB, the number of decoding attempts being stored in a decodingattempt counter; if the number of decoding attempts for the first TB isequal to a decoding attempt threshold, the base station that found theerror further determines if the first TB is a discontinuous transmissionframe (DTX) or a TB including errors; and if the base station determinesthat the first TB is a DTX, the base station that found the errorfurther resets the decoding attempt counter and prepares the station fora new, second TB.
 2. The method according to claim 1, wherein the firstbase station interprets the DTX in the Transmission Time Interval (TTI)when the first TB would have been transmitted as an indication that thefirst TB has been successfully decoded at least by the second basestation.
 3. The method according to claim 2, wherein the first basestation when interpreting the transmission of the DTX as an indicationof a successful decoding suppress the sending of a failure indication tothe RNC.
 4. The method according to claim 1, wherein if the base stationdetermines that the first TB is a TB that includes errors, the basestation that found the error further transmits a failure indication tothe RNC, comprising the first TB including the error.
 5. The methodaccording to claim 4, wherein the RNC checks the Block Error Rate (BLER)ratio on the first TB transmitted from the base station and determines asignal to interference ratio (SIR) target on the basis of the BLER. 6.The method according to claim 3, wherein the failure indication consistsin a Hybrid Automatic Repeat Request (HARQ) failure indication.
 7. Themethod according to claim 1, wherein if no error in the first TB isfound by the first and/or the second base station, the base stationtransmit a success indication to the RNC, comprising the first TBcontaining no errors.
 8. The method according to claim 1, wherein thedetermination of DTX by the base station that found the error is atleast based on the signal strength or signal to noise ratio whentransmitting the first TB.
 9. The method according to claim 8, whereinthe signal strength or signal to noise ratio is determined by the basestation by accumulating the received signal energy or measuring thereceived signal power.
 10. The method according to claim 8, wherein athreshold for signal strength used to indicate the presence of DTXdepends on whether the signal strength or the signal to noise ratio isissued.
 11. A base station adapted for power control in an enhanceduplink (UL) telecommunication system further comprising: at least onefirst radio network controller (RNC), at least one first and one secondbase station in the system enabling wireless communication with at leastone first user terminal, wherein the first and the second base stationsbeing adapted to receive at least a first transport block (TB), thefirst TB being transmitted by the user terminal over an establishedcommunication channel, the first (11) and the second (10) base stationfurther being adapted to control whether the received first TB includesat least one error, if at least one error in the first TB is found bythe first (11) and/or the second (10) base station, the base stationthat found the error further being adapted to control the number ofdecoding attempts for the first TB, the number of decoding attemptsbeing stored in a decoding attempt counter, if the number of decodingattempts for the first TB is equal to a decoding attempt threshold, thebase station/-s (10,11) that found the error is further adapted todetermine if the first TB is a discontinuous transmission frame (DTX) ora TB including errors and if the first TB is a DTX, the base stationthat found the error is further adapted to reset the decoding attemptcounter and prepares the station for a new, second TB.
 12. The basestation according to claim 11, wherein the first base station is adaptedto interpret the DTX in the Transmission Time Interval (TTI) when thefirst TB would have been transmitted as an indication that the first TBhas been successfully decoded at least by the second base station. 13.The base station according to claim 12, wherein the first base stationwhen interpreting the transmission of the DTX as an indication of asuccessful decoding is further adapted to suppress the sending of afailure indication to the RNC.
 14. The base station according claim 11,wherein if the base station determines that the first TB is a TB thatincludes errors, the base station that found the error is furtheradapted to transmit a failure indication to the RNC, comprising thefirst TB including the error.
 15. The base station according to claim13, wherein the failure indication consists in a Hybrid Automatic RepeatRequest (HARQ) failure indication.
 16. The base station according toclaim 11, wherein if no error in the first TB is found by the firstand/or the second base station, the base station is adapted to transmita success indication to the RNC, comprising the first TB containing noerrors.
 17. The base station according to claim 11, wherein the basestation that found the error is adapted to determine DTX at least basedon the signal strength or signal to noise ratio when transmitting thefirst TB.
 18. The base station according to claim 17, wherein the basestation is further adapted to determine the signal strength or signal tonoise ratio by accumulating the received signal energy or measure thereceived signal power.
 19. The base station according to claim 17,wherein a threshold for signal strength used to indicate the presence ofDTX depends on whether the signal strength or the signal to noise ratiois issued.
 20. An enhanced uplink (UL) telecommunication system adaptedfor power control, the system comprising: at least one first radionetwork controller (RNC) and at least one first and one second basestation enabling wireless communication with at least one first userterminal, wherein the first and the second base stations being adaptedto receive at least a first transport block (TB), the first TB beingtransmitted by the user terminal over an established communicationchannel, the first and the second base station further being adapted tocontrol whether the received first TB includes at least one error, if atleast one error in the first. TB is found by the first and/or the secondbase station, the base station that found the error further beingadapted to control the number of decoding attempts for the first TB, thenumber of decoding attempts being stored in a decoding attempt counter,if the number of decoding attempts for the first TB is equal to adecoding attempt threshold, the base station that found the error isfurther adapted to determine if the first TB is a discontinuoustransmission frame (DTX) or a TB including errors, and if the first TBis a DTX, the base station/-s that found the error is further adapted toreset the decoding attempt counter and prepares the station/-s for anew, second TB.
 21. The base station according to claim 20, wherein thefirst base station is adapted to interpret the DTX in the TransmissionTime Interval (TTI) when the first TB would have been transmitted as anindication that the first TB has been successfully decoded at least bythe second base station.
 22. The base station according to claim 21,wherein the first base station when interpreting the transmission of theDTX as an indication of a successful decoding is further adapted tosuppress the sending of a failure indication to the RNC.
 23. The basestation according to claim 20, wherein if the base station determinesthat the first TB is a TB that includes errors, the base station thatfound the error is further adapted to transmit a failure indication tothe RNC, comprising the first TB including the error.
 24. The basestation according to claim 22, wherein the failure indication consistsin a Hybrid Automatic Repeat Request (HARQ) failure indication.
 25. Thebase station according to claim 20, wherein if no error in the first TBis found by the first and/or the second base station, the base stationis adapted to transmit a success indication to the RNC, comprising thefirst TB containing no errors.
 26. The base station according to claim20, wherein the base station that found the error is adapted todetermine DTX at least based on the signal strength or signal to noiseratio when transmitting the first TB.
 27. The base station according toclaim 26, wherein the base station is further adapted to determine thesignal strength or signal to noise ratio by accumulating the receivedsignal energy or measure the received signal power.
 28. The base stationaccording to claim 26, wherein a threshold for signal strength used toindicate the presence of DTX depends on whether the signal strength orthe signal to noise ratio is issued.